1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing cut-pile fabrics having improved wear properties. More specifically, the invention relates to a method and apparatus for ultrasonically cutting carpet pile loops in such a way that fusion of the filaments at the tips of the yarn tufts occurs, resulting in improved resistance to matting and tip-flaring.
2. Prior Art
Currently available cut-pile carpets have a relatively short lifetime in high-traffic areas where they quickly become matted and "ugly-out", losing their appearance of newness. Several methods of improving texture retention and wear properties are known in the art. Increasing carpet density improves durability somewhat but is costly. Hatt, U.S. Pat. No. 3,900,623, discloses a carpet in which a large portion of the filaments in and near the tops of the pile tufts are highly interlaced which gives improved retention of tuft identity and substantially prevents tip-flaring after prolonged use in traffic. The use of heat-activated binder fibers in carpet yarns to improve retention of tuft identity is disclosed in the published patent applications Hackler PCT-WO 88/03969 and Watt & Fowler GB 2205116-A. The binder fibers melt during twist-setting and bond the filaments of the yarn together resulting in improved twist retention and enhanced wear properties.
Cut-pile carpets are currently manufactured by tufting loops of carpet yarn into a primary backing on a tufting machine. A knife cuts the loops as they are formed to give a cut-pile carpet. The carpet is dyed, and latex and a secondary backing are then applied. The carpet is then trimmed to the correct width and sheared using revolving shearing blades to remove fuzz and to cut any fibers which are longer than the desired pile height to yield a smooth and even surface.
The present invention relates to the use of ultrasonic vibrational energy to simultaneously cut and fuse yarn loops of a pile fabric. The use of a focussed laser beam to cut thread loops of a pile fabric by combustion is disclosed in Durville et al., U.S. Pat. No. 4,271,568. Seiler & Zurcher, published application EP 0097618, discloses methods for cutting filaments or fibers by heating with a laser beam while subjecting the fibers to a tensile stress such that fibers are drawn before rupturing, resulting in a pointed end at the tips of the filaments. Neither of these references discloses the fusion of a number of filament bundles, such as in a carpet tuft, during the cutting process.